Many stacking devices are used to continuously create stacks of sheet products. In one common stacking device, the sheets are fed from a feeding system to the top of a wheel that is rotated about a wheel axis. The wheel includes a plurality of spiraled wheel blades or fins that project in a direction opposite to the direction of rotation. The sheets are fed between two adjacent fins and are rotated within the wheel to a lower position where the paper is stripped from the wheel by a barrier. The stripped sheets fall away from the wheel onto a stacking plate located at the bottom of a stacking box. Different separators have been developed to separate two adjacent sheets being discharged from the wheel. The two adjacent sheets include a sheet that completes the stack of a specified number located in the stacking box and another sheet that begins a new stack on the separator.
For example, some stacking devices rotate a separator about an axis that is displaced from the wheel axis but within the periphery of the wheel. The separator is rotated into a position between a first fed sheet that has just been fed into the wheel and an adjacent second sheet that will be fed into the wheel behind the separator as the wheel and separator rotate in the same direction. The separator rotates to the stacking position where the separator allows the first fed sheet to complete the stack located in the stacking box and supports the second fed sheet to begin a new stack at a position above the stacking plate of the stacking box. The separator accumulates additional sheets of the new stack to allow the completed stack to be sent to downstream operations, such as a packaging or bundling unit. When the stacking plate of the stacking box is cleared and ready to receive the new sheets accumulated by the separator, the separator rotates through the stacking box causing the sheets to fall onto the stacking plate located at the bottom of the stacking box.
In the above-described device, the separator can strike the sheets that are not fully seated between the blades because the travel path of the separator intersects with the travel path of the blades. This undesirable contact is caused by rotating the separator about a different rotational axis than the wheel axis which causes portions of the path traveled by the separator to intersect the path traveled by the sheets carried on the wheel.
Another type of conventional stacking device rotates a separator about the same axis as the wheel axis. The separator is coupled by an arm to the wheel axis, however the separator is at all times located outside a cylindrical volume that is defined by the periphery of the wheel. The separator rotates to a stacking position between a first sheet has been discharged from the wheel into the stacking box and a second sheet that is still located within the wheel. The separator allows the first sheet to fall to complete the stack located on a stacking plate in the stacking box while the separator supports the second sheet above the completed stack as it is discharged from the wheel. The separator will support additional sheets while the stacking plate moves the completed stack to another location. The separator is limited to supporting only as many sheets as space permits because the separator is located a fixed distance from the periphery of the wheel. After the stacking plate returns to the stacking box and the stacking box is ready to accept the partially completed stack from the separator, the separator is rotated about the common axis. As the separator is rotated the barrier will strip the sheets from the separator and the sheets will fall onto the stacking plate that is located at the bottom of the stacking box.
Another type of conventional separating device includes a separator that rotates about the wheel axis and moves radially away from the wheel axis once it is in the stacking position in order to accumulate additional sheets. The separator is rotated into a position between a first sheet that has just been fed into the wheel and a second sheet that will be fed into the wheel behind the separator as the wheel and separator rotate at the same speed about the common axis. The separator is rotated with the wheel until the separator is located at the stacking position beneath the wheel. The separator allows the first sheet to fall and complete the stack positioned on the stacking plate of the stacking box and supports the second sheet to begin the new stack on the separator. The separator finger moves radially away from the wheel to support additional sheets. Moving away from the wheel creates additional space to allow the separator to support more sheets than would be possible with a separator that did not move radially from the wheel. The stacking plate therefore has more time to move the completed stack because the separator can support an increased number of sheets before they must be transferred onto the stacking plate of the stacking box. When the stacking plate returns to the stacking box and is ready to accept the stack from the separator, the separator will rotate causing the barrier to push the sheets from the separator. The sheets then fall onto the stacking plate that is located at the bottom of the stacking box.
Separators that are rotatably connected to the wheel axis often require a complex design that is limited in space about the axis of rotation of the wheel. The complexity of this configuration increases the cost of manufacturing and assembly costs associated with the separator. Inaccessibility of the components of such an intricate and compact design also tends to increase the maintenance and repair costs of the separator.
Known separators used with starwheel assemblies are typically employed to separate sheets discharged from the bottom of a starwheel, thereby vertically stacking the sheets. In this configuration, the stacks normally only need to be supported from the bottom of the stack, such as by the separator itself or by a separate stacking plate or other support. Stacks produced in this manner are commonly referred to as “down packs” or “small packs”, and typically contain from ten to one hundred napkins per stack (although other stack counts are possible).
In other cases, separators are employed to separate sheets discharged laterally from starwheel assemblies, thereby stacking the sheets horizontally with each of the sheets being vertically oriented. Stacks generated from sheets discharged laterally from starwheel assemblies are typically supported at both ends of the stack and along the bottom edge of the stack. Stacks produced in this manner are commonly referred to as “bulk packs” and typically contain several hundred napkins, often between 250 and 600 napkins (although other stack counts are possible).
Historically, it has proven to be more difficult to separate a continuous horizontal stream of sheets into stacks of sheets because the stacks must be supported from both ends of the stack while being moved from the starwheel. One known method employed to overcome this difficulty is to use a stacking apparatus having two starwheel assemblies fed sheets from two respective infeed conveyors. The stacking apparatus also includes a diverter upstream of the feed conveyors and starwheel assemblies in order to selectively direct an incoming stream of sheets to one of the two infeed conveyors. In operation, one starwheel assembly is fed sheets from one infeed conveyor until a stack of a desired number of sheets is created. The diverter is then activated to redirect the incoming stream of sheets to the other infeed conveyor and into the other starwheel assembly so that the completed stack can be removed without interfering with additional sheets that would otherwise be discharged from the starwheel. This method of separating a continuous horizontal stream of stacked sheets is disadvantageous because it requires two starwheel assemblies—only one of which is operated at a given time. As a result, this method increases machinery cost, maintenance, and the amount of floor space required for such machinery.
In light of the above design requirements and limitations, a need exists for an apparatus and method for discharging sheets from a starwheel assembly and separating the sheets with a separator that controllably moves between two adjacent sheets within the starwheel without adversely affecting the position or movement of the sheets within the starwheel assembly, a separator that can move efficiently to enable the use of a simpler and less costly machine design, a separator that is mounted to the frame outside of a cylindrical volume defined by the periphery of the wheel to simplify the design and manufacture, a separator that creates and allows removal of stacks from a continuous stream of discharged sheets, and a relatively simple separator design that can lower separator manufacturing, maintenance, and/or repair costs, and a manner in which to stack and separate sheets laterally discharged from a starwheel assembly. Each preferred embodiment of the present invention achieves one or more of these results.